Page 64 - BBC Sky at Night - September 2017 UK

64 SEPTEMBER THE SKY GUIDE

ASTROPHOTOGRAPHY

The thinnest of lunar crescents

beautiful view. This is an excellent
RECOMMENDED EQUIPMENT training session for tomorrow’s Moon.
DSLR with shutter release cable, telescope or lens, tripod or tracking mount On the morning of 18 September, at the
recommended for longer focal lengths same time you ventured out on the 17th,
things will have changed. The Moon’s
crescent will now be noticeably thinner
at 4% lit. The Moon’s position will also
have changed so that it now sits between
Venus and the Mercury-Mars pair. Mag.
+1.4 Regulus (Alpha (_) Leonis) is also
visible 0.25º north of the Moon’s
northern limb. Despite being thinner,
this Moon shouldn’t give too many
problems for photography. It’ll still
have a decent altitude in reasonably
dark twilight and should be relatively
easy to frame and focus.
On 19 September, big changes will
be apparent. Mercury and Mars will
now appear separated by four times
the Moon’s apparent diameter. The
Moon’s crescent will now be only
1.3% lit and it will lie below and left
of Mercury. Use the Mars-Mercury

You can start watching the line to locate it, extending that line
waning crescent Moon a couple by roughly twice the distance again,
of days before the thinnest down towards the horizon.
one and see its phases shrink By carefully noting the settings
you used on previous mornings it
Photographing the thin crescent 50 minutes before the Sun pops up should be possible to achieve a
Moon is both challenging and great above the horizon. From the centre convincing shot of this thin waning
fun. There are two opportunities in of the UK, this means a 06:00 BST crescent Moon. If the weather holds,
any given month, one for the waxing (05:00 UT) start. The 11.1% lit waning and you do manage to grab a shot of it,
crescent in the evening twilight sky crescent Moon will be 10º above and as well as having a trophy of the Solar
and one for the waning crescent in right of brilliant planet Venus, over System to keep, you’ll feel a definite
the morning. Not all occurrences are in the east. Mars and Mercury are there sense of achievement. Good luck!
favourable, however. During the spring too, a similar distance from Venus in
months, it’s the waxing crescent Moon the opposite direction to the Moon.
that’s best placed, the waning one These planets will be in close proximity KEY TECHNIQUE
tending to be too close to the horizon to one another this morning and a SWIFT SETTING CHANGES
as the Sun rises. During autumn lovely sight to photograph in their Imaging a thin waxing or waning crescent
the tables turn and it’s the waning own right. Compare their separation Moon is challenging. Appearing against
crescents that are easier to see. to the diameter of the Moon: on the a bright twilight, the delicate crescent is
easily lost both to the eye and to the
In many ways hunting the waning 17th they will be two-thirds the
camera. Choosing the right settings here
crescent is more useful than its waxing Moon’s apparent diameter apart.
is essential as is keeping a constant eye
counterpart, the reason being that This Moon is a relatively easy target on the camera’s preview screen. Adjusting
spotting a thin waning crescent provides to photograph. Take your time, focus as settings on the fly is a key skill that
training to spot and even thinner one accurately as possible and take your shot. astrophotographers have to master and
the next morning. With waxing crescents As indicated in our step-by-step guide, here the technique is pushed to the limit.
With mastery over the settings it’s often
the thinnest event happens first. Miss it make sure you don’t overexpose the possible to use the camera in thin Moon
ALL PIUCTURES: PETE LAWRENCE easier. This month there is a golden at the brightest points is fine. Make a when it’s not visible to the naked eye.
lunar surface to white. Just below white
and the next night it becomes a little
situations to record the crescent even
opportunity to catch a 1.3%-lit waning
note of your settings and take in that
crescent Moon on 19 September.
Start two days before, on the morning

Send your image to: hotshots@skyatnightmagazine.com
of the 17th. Aim to make your attempt
skyatnightmagazine.com 2017